let watermark = {};

let setWatermark = (str) => {
  let id = "1.23452384164.123412416";

  if (document.getElementById(id) !== null) {
    document.body.removeChild(document.getElementById(id));
  }

  //创建一个画布
  let can = document.createElement("canvas");
  //设置画布的长宽
  can.width = 400;
  can.height = 300;

  let cans = can.getContext("2d");
  //旋转角度
  cans.rotate((-15 * Math.PI) / 180);
  cans.font = "18px Vedana";
  //设置填充绘画的颜色、渐变或者模式
  cans.fillStyle = "rgba(200, 200, 200, 0.60)";
  //设置文本内容的当前对齐方式
  cans.textAlign = "center";
  //设置在绘制文本时使用的当前文本基线
  cans.textBaseline = "hanging";
  //在画布上绘制填色的文本（输出的文本，开始绘制文本的X坐标位置，开始绘制文本的Y坐标位置）
  cans.fillText(str, can.width / 8, can.height / 6);
  cans.fillText("内部信息,禁止外传", can.width / 4, can.height / 2);

  let div = document.createElement("div");
  div.id = id;
  div.style.pointerEvents = "none";
  div.style.top = "30px";
  div.style.left = "0px";
  div.style.position = "fixed";
  div.style.zIndex = "100000";
  div.style.width = document.documentElement.clientWidth + "px";
  div.style.height = document.documentElement.clientHeight + "px";
  div.style.background = "url(" + can.toDataURL("image/png") + ") left top repeat";
  document.body.appendChild(div);
  return id;
};

// 该方法只允许调用一次
watermark.set = (str) => {
  let id = setWatermark(str);
  setInterval(() => {
    if (document.getElementById(id) === null) {
      id = setWatermark(str);
    }
  }, 500);
  window.onresize = () => {
    setWatermark(str);
  };
};

export default watermark;

